Existing, standard low-power plug-in chargers are made by many manufacturers and are in widespread use. These chargers have no automatic control to disconnect the transformer primary from AC power. These systems consume energy as long as they are plugged in, whether or not the system is operating.
More generally, existing power supplies result in parasitic non-operating energy waste. An offline power supply continues to consume energy as long as the system is plugged-in, even when the system for which power is being supplied is not operational, such as when the system is off, battery is fully charged, etc.
Examples of such systems include power supplies for laptop computers, plug-in battery chargers for hand-held electronic devices such as cell phones, portable music players. Any “instant on” device that responds to remote control units, such as television sets, cable boxes, also continues to consume energy even when the unit is turned off. This is necessary to allow the unit to be able to respond to the remote control signal.
Put another way, as long as there is an AC transformer plugged into the AC power source, the unit will consume energy. The only way to stop this parasitic power consumption is to remove the AC power source. Removing the AC power source usually requires unplugging the unit from the AC socket. This may be an inconvenience and many users leave units plugged in all the time, resulting in considerable waste of energy when considered across the distribution of households on a continual basis.
An existing high power (200-400 VDC) charger has a switch (transistor) on the primary side of the transformer for control. Since a control signal is necessary to activate this switch and energize the transformer, the system requires an existing battery charge to be present in order to initialize the charger system operation.
Background information may be found in U.S. Pat. Nos. 7,894,212, 6,445,268, 6,198,638, 5,390,101, 6,061,257, and 7,295,449. Further background information may be found in U.S. Pub. Nos. 2003/0210118, 2008/0061746, 2006/0062027.